An ammonia-responsive aerogel-type colorimetric sensor for non-destructive monitoring of shrimp freshness

The colorimetric sensor for volatile amines (VA) detection can realize non-destructive monitoring of shrimp quality. However, its sensing performance still needs to be improved. In this study, we proposed an aerogel-type colorimetric sensor to improve VA sensing performance and realize early detection of shrimp spoilage. The sensor was composed of konjac glucomannan-based aerogel prepared by sol-gel and freeze-drying, and pH-responsive dyes (neutral red) which were adsorbed on the aerogel surface. The sensor could show color change from pink to orange under the exposure of NH3, a marker of spoiled shrimp and the Euclidean Distance (Delta E) of the sensor was positively correlated with NH3 concentration. Due the three-dimensional network of the aerogel and its adsorption performance, the sensitivity of the aerogel-type sensor in NH3 detection was similar to 6 times higher and the maximum Delta E was similar to 1.5 times higher compared with the film-type sensor. It also showed stable sensing performance under various environment and was further successfully used in shrimp freshness monitoring. It was found that Delta E higher than 23.88 indicated the spoilage of shrimp. The above results provided a general approach for the designing of high-performance colorimetric sensor for real-time and non-destructive monitoring of shrimp freshness.